The molecular identification of staphylococcus aureus from cows with mastitis and determination of antibiotic susceptibilies

Objective: The objective of this study was to investigate Staphylococcus aureus (S. aureus) from cows with mastitis, to investigate the nuc, mecA and blaZ genes in isolated strains by Polymerase Chain Reaction method (PCR) and to determine the resistance of strains to various antibiotics commonly used in the veterinary field. Material and Methods: A total of 57 milk samples were collected from 41 animals with clinical mastitis from farms located in and around the central district of Aydın. Following the isolation and identification stages, Staphylococcus sp. DNA extractions of the biochemically identified isolates were performed and antibiotic resistance genes were genotypically investigated by PCR. Antibiotic susceptibility/resistance of strains identified as S. aureus and Coagulase Positive Staphylococci were determined as recommended by CLSI criteria. Results: Fifteen (26.3%) Coagulase Positive Staphylococci were isolated from 57 milk samples. As a result of the genotypic identification of Coagulase Positive Staphylococci, 6 (10.5%) were identified as S. aureus. Bacterial growth was not detected in a total of 22 (38.6%) samples. As a result of PCR, products with a length of 270 and 517 bp were obtained in Coagulase Positive Staphylococcus isolates. Six of the 15 isolates identified as coagulase positive were confirmed as S. aureus. blaZ gene was found in 2 of 6 isolates. MecA gene was not found in any of the isolates. As a result of the antibiogram test, S. aureus isolates are shown to be 100% resistant to Penicillin G, Sulfomethoxazole-Trimethoprim and Amoxicillin-clavulanic acid, 100% sensitive to Vancomycin and Clindamycin, 83% to Polymyxin B, Cefoperazone and Oxacillin and 50% to Enrofloxacin. Conclution: As a result, S. aureus identification was 10.5% in this study. Our research has revealed the potential for use of Polymyxin B as an alternative mastitis therapeutic agent. Polymixin B is shown to be a promising alternative agent to combat staphylococcal infections.